Hub gmail dDropbox pdf attachment weirdness

So I go to the hub, select compose, select gmail, type a recipient's address, subject, write some text, choose attachment which opens the file manager, choose dropbox, select a pdf file, press send.... And my message disappears, doesn't show up in sent or outbox... Nor in those folders if I sign in online.

If I do the same with any other type of file, no problems, the email goes out. I can also go into the file manager, then dropbox, select the pdf and select share via gmail, that works. And if I chose Hub attachment, that does work too, if the pdf happens to be a hub attachment I guess. Just not from composing from the Hub.

I did a search but came up with older problems previous to the latest release. Any ideas?